Why one of the world's largest digital banks chose Clojure

Nubank co-founder Edward Wible and distinguished engineer Lucas Cavalcanti explain why the fintech giant chose Clojure as its primary backend language. Inspired by the 'Out of the Tar Pit' paper, the founding team concluded that mutable state and side effects are the root of accidental complexity in large systems. This led them to Clojure's functional programming model and Datomic's immutable database, which offered time-travel queries and full audit history — a natural fit for banking's regulatory requirements. Clojure's JVM foundation also gave access to the mature Java library ecosystem, letting the team focus on business problems rather than rebuilding infrastructure.